Bump, finally finished it.
Sprayed in warnex - which was a learning curve. For those in the UK I used a 3hp compressor, a machine mart pressurised paint pot and Clarke pro 18c gun. I wasted a load of paint by not having enough air flow to do the base coat meaning it spattered first. Got there eventually. Think I'd use tuff cab in the future though.
Tried to do a good job, all mounting hardware is chemically black steel, shake proofs used. An nl2 socket is in the slot to connect the slot driver, all spades are locking type and soldered. Socket plate was sprayed in gloss, I will make a spec plate for it some time.
Massive respect to those who have built complete systems this was a mission for one sub and one mid high I built at the same time.
Sprayed in warnex - which was a learning curve. For those in the UK I used a 3hp compressor, a machine mart pressurised paint pot and Clarke pro 18c gun. I wasted a load of paint by not having enough air flow to do the base coat meaning it spattered first. Got there eventually. Think I'd use tuff cab in the future though.
Tried to do a good job, all mounting hardware is chemically black steel, shake proofs used. An nl2 socket is in the slot to connect the slot driver, all spades are locking type and soldered. Socket plate was sprayed in gloss, I will make a spec plate for it some time.
Massive respect to those who have built complete systems this was a mission for one sub and one mid high I built at the same time.
Attachments
Bump.
Cab number 2 in production. Taught myself some CAD and put a lot more work into the drawings to make the CNC router do more work. Rebated the side panels, new handle design to help loading, and more intricate main brace.
One was good but 2 has to be better!
Cab number 2 in production. Taught myself some CAD and put a lot more work into the drawings to make the CNC router do more work. Rebated the side panels, new handle design to help loading, and more intricate main brace.
One was good but 2 has to be better!
Attachments
All built, warnex is in, when the back is better it will get painted. I don't like the look of corners but I might have to add them. I'll keep with my macro tech 2402 but in parallel mono.
https://goo.gl/photos/yKJKFMibTBJ32mcq8
https://goo.gl/photos/yKJKFMibTBJ32mcq8
Attachments
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PPSL sound very different than the usual PA sub, much, much cleaner.
As a result, they sound like they go deeper (even though they don't measure as going any deeper).
I suggest listening to a hi-fi servo sub to get an idea of how they sound. If you don't like a Velodyne servo sub (or other similar servo type), you probably won't like a PPSL.
A friend of mine converted one of his Klipsch LaScala to PPSL, we were astonished at the difference in sound, the other one was converted posthaste.
As a result, they sound like they go deeper (even though they don't measure as going any deeper).
I suggest listening to a hi-fi servo sub to get an idea of how they sound. If you don't like a Velodyne servo sub (or other similar servo type), you probably won't like a PPSL.
A friend of mine converted one of his Klipsch LaScala to PPSL, we were astonished at the difference in sound, the other one was converted posthaste.
"Is there any difference in efficiecy compared to a front loaded BR?"
Not really, maybe a bit more at higher frequencies (100hz and up).
Nelson Pass measured a ~2.5dB increase on his SLOB (with a similar compression ratio in the slot as used in my first dual 15 PPSL), but I have just recently acquired the better test gear that I needed to make such measurements (I have been using a 30 year old RTA and/or 1/3 oct warbletones.)
The main gain is in 6th order vented, vs 4th order vented, or 2nd order sealed.
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
Not really, maybe a bit more at higher frequencies (100hz and up).
Nelson Pass measured a ~2.5dB increase on his SLOB (with a similar compression ratio in the slot as used in my first dual 15 PPSL), but I have just recently acquired the better test gear that I needed to make such measurements (I have been using a 30 year old RTA and/or 1/3 oct warbletones.)
The main gain is in 6th order vented, vs 4th order vented, or 2nd order sealed.
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
re-visit compression ratios ?
I'm getting ready to start another ppsl project. This time it will be strictly for sub woofer frequencies. Dennis, if you could please save me some time searching; I need to know if an exit which is .360 x the SD of one driver is okay ? I need to maximize the benefit of the close coupling. The driver(s) in question are the Dayton PA-380. Thanks in advance.
p.s. for reference: in my mid bass project, I used a .5 exit. It turned out to be excellent. (Eminence 4012HO)
I'm getting ready to start another ppsl project. This time it will be strictly for sub woofer frequencies. Dennis, if you could please save me some time searching; I need to know if an exit which is .360 x the SD of one driver is okay ? I need to maximize the benefit of the close coupling. The driver(s) in question are the Dayton PA-380. Thanks in advance.
p.s. for reference: in my mid bass project, I used a .5 exit. It turned out to be excellent. (Eminence 4012HO)
I am using 8 drivers for this project. My old memory storage (aka preserved brain cells)tells me a 15 has 133 sq. inches. The planned plenum dimensions are 6x64. 6x64= 384, 133x8= 1064, 384 divided by 1064= .36090
Thanks for your prompt reply, as I am starting this project tomorrow.
My original prototype had a 5" x 16.5" slot (and a removable loading doors for mounting the drivers), a 0.31 ratio.
I increased the slot width mainly to eliminate the loading doors.
I was a little alarmed at the high pressure, but a Klipschorn/LaScala/Belle has a slightly higher compression ratio without a issues.
I increased the slot width mainly to eliminate the loading doors.
I was a little alarmed at the high pressure, but a Klipschorn/LaScala/Belle has a slightly higher compression ratio without a issues.
I'm not sure if I understand what 6th order refers to in this case.
1. Is it an electrical aligment (EQ circuit) just extending the low cutoff but not providing any better efficiency over the whole usable passband?
2. Or, is it an acoustical loading?
I guess it's the first as I don't see a second chamber vented. But not sure about the function of the manifold slot.
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"I'm not sure if I understand what 6th order refers to in this case. "
Optimum would be an SBB4 with a Qts=0.312 and a two-pole high-pass filter with a Q=2 at Fb (which is also the Fs of the driver, and becomes the F3 point of the system).
BassBoxPro v6 will model these type of systems, even with non-optimum Qts drivers.
http://xlrtechs.com/dbkeele.com/papers.htm
I started building 6th order vented systems in 1974 (after EV lead the way).
Most of the B&W 800 series are 6th order (hi-fi).
"But not sure about the function of the manifold slot. "
Getting the drivers close for the distortion reduction, reaction cancellation (box does not 'walk').
Optimum would be an SBB4 with a Qts=0.312 and a two-pole high-pass filter with a Q=2 at Fb (which is also the Fs of the driver, and becomes the F3 point of the system).
BassBoxPro v6 will model these type of systems, even with non-optimum Qts drivers.
http://xlrtechs.com/dbkeele.com/papers.htm
I started building 6th order vented systems in 1974 (after EV lead the way).
Most of the B&W 800 series are 6th order (hi-fi).
"But not sure about the function of the manifold slot. "
Getting the drivers close for the distortion reduction, reaction cancellation (box does not 'walk').
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Several concepts I wish to adress here
In a small and very well built plenum (STURDY), the drivers operate in a vibration cancelling mode. The enclosure walls do not receive transmitted vibrations from the drivers, but they are still susceptible to the pressures that are created. The resulting bass quality is quite remarkable, in that, very little energy is lost in translation as compared to conventional boxed woofers. I hear this every single time I go to audition these "conventional" systems. I call it "bass blurr". By contrast, when others visit mine, since it is so clean, clear and distortion free, often times they proclaim something is "missing?"
With further observations regarding the plenum output; there is at least one other contributor on this forum who maintains the plenum projects a pressurized wave front several feet in front of said enclosure, and it is for this reason, the ppsl mates so well with the horns that are often times used for mids/highs.
With respect to my current ppsl low frequency project, I wish to further investigate my "theory" that push-pull, slot loading, does a couple of things:
Lowers the driver's inherent Fs, and also raises Qts (??). I am using relatively low cost drivers, albeit in multiples, just to see (out of curiosity), how close I can get in performance, with a large vented enclosure, as compared to my HUGE existing infinite baffle sub woofer system with an F3 of 24 Hz as measured in-room, near field, no BS claims.
In a small and very well built plenum (STURDY), the drivers operate in a vibration cancelling mode. The enclosure walls do not receive transmitted vibrations from the drivers, but they are still susceptible to the pressures that are created. The resulting bass quality is quite remarkable, in that, very little energy is lost in translation as compared to conventional boxed woofers. I hear this every single time I go to audition these "conventional" systems. I call it "bass blurr". By contrast, when others visit mine, since it is so clean, clear and distortion free, often times they proclaim something is "missing?"
With further observations regarding the plenum output; there is at least one other contributor on this forum who maintains the plenum projects a pressurized wave front several feet in front of said enclosure, and it is for this reason, the ppsl mates so well with the horns that are often times used for mids/highs.
With respect to my current ppsl low frequency project, I wish to further investigate my "theory" that push-pull, slot loading, does a couple of things:
Lowers the driver's inherent Fs, and also raises Qts (??). I am using relatively low cost drivers, albeit in multiples, just to see (out of curiosity), how close I can get in performance, with a large vented enclosure, as compared to my HUGE existing infinite baffle sub woofer system with an F3 of 24 Hz as measured in-room, near field, no BS claims.
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